Renal synthesis and secretion of renin will be studied in dogs and rats. By following the incorporation of H3 leucine into renin, we can determine the rate of renin synthesis. Renal slices, incubated in physiological saline to which H3 leucine is added, will be the system used. Gel electrophoresis is used to isolate the band containing renin. Radioactivity in that band is measured. Simultaneously the rate of renin secreted into the medium is measured. Thus, we can measure simultaneously the rate of synthesis and secretion to a wide variety of stimuli. Other experiments will be done in order to define the stimuli which initiate renal hypertrophy. By measuring both physiological (GFR, RPF, UNaV, etc.) hypertrophy and biochemical (DNA and RNA content) in the same rats, we can define the process better. We now know that the two do not proceed simultaneously. It is possible to obtain evidence of biochemical hypertrophy without concomitant physiological hypertrophy. This model will be studied in a variety of situations which stress the kidney: salt loading, unilateral nephrectomy, unilateral ureteral ligation. BIBLIOGRAPHIC REFERENCES: Mulcahy, J.J., Geis, W.P., & Malvin, R.L., The Effects of Cardiac Derivation on Renal Function. Proc. Exptl. Biol. & Med. 149:422-426, 1975. Opava-Stetzer, S. & Malvin, R.L., Right Atrium & Renal Sodium Excretion. Am. J. Physiology. 228:184-190, 1975.